The present invention relates to a fin-and-tube heat exchanger wherein a heat exchanger tube extends through a fin plate.
FIG. 23 is a vertical cross-sectional view showing the structure of a conventional fin-and-tube heat exchanger as shown in e.g. Japanese Unexamined Patent Publication No. 28991/1983. In FIG. 23, reference numeral 1 designates a heat exchanger tube. Reference numeral 2 designates a fin plate. Reference numeral 3 designates a tube-receiving collar which is formed in the fin plate 2, and which the heat exchanger tube 1 is fitted in and thermally connected to. Reference numerals 4 and 5 designate longitudinal louvers which are slitted and bent from the fin plate 2, constituting a shorter slit and a longer slit, respectively. Reference numerals 2a and 2b designate a leading edge and a trailing edge with respect to the flow direction A of a fluid.
The heat exchanger is constructed as a cross fin tube heat exchanger wherein banks of straight tubular portions (portions of the heat exchanger tube 1) are arrayed in a zigzag or grid pattern with respect to the fin plate 2, and the louvers 4 and 5 having a narrow width are provided at the fin plate 2 so as to be perpendicular to the flow direction A of the fluid. The louvers 4 and 5 are symmetrical with respect to a central line of the tube bank in the vertical direction. The width L.sub.1 of non-slitted part which is located at a central position between the adjacent vertical tube banks is twice the width L.sub.2 of the parts which are located between the leading edge 2a of the plate 2 and the louver nearest to the leading edge and between the trailing edge 2b and the louver nearest to the trailing edge. The same press die is used to shape one sheet, two sheets, three sheets or more of the fin plate 2 so that the assembled fin plates can be balanced against the blast output of an air conditioner and so on. A plurality columns of the fin plates can be used to construct a heat exchanger for an air conditioner with a dehumidifying function. In a similar way, the heat exchanger having the banks of the straight tubular portions arrayed in a zigzag or grid pattern can be easily obtained. In addition, heat transfer efficiency of the fin plate 2 can be increased, and flow loss of the plate can be decreased.
Because the conventional heat exchanger is constructed as stated earlier, a stagnant fluid zone B, e.g. stagnation of the fluid can be generated behind the heat exchanger tube 1 in the flow direction A of the fluid, and heat transfer performance is remarkably lowered in the stagnant fluid zone B of the fin plate 2, creating a problem wherein heat transfer performance of the whole heat exchanger is lowered. In addition, there is another problem wherein resistance to the fluid caused by the shape of the heat exchanger tube 1 is great to increase fluid loss because the stagnant fluid zone B is big.